JP2014111334A - Droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a droplet discharge device capable of reducing air bubbles accumulated in a circulation channel or a dead water region of a droplet discharge part while suppressing discharge of unexpected liquid from a discharge port in an air bubble reduction mode.SOLUTION: An inkjet recording device 10 comprises: a head module 50; a circulation channel 100 including a supply channel 30 and an ejection channel 60; a supply side pump 118 and a recovery side pump 149 provided at the circulation channel 100; and a micro computer 202. The micro computer 202 switches from a normal mode for discharging an ink droplet LA to an air bubble reduction mode for circulating ink L without discharging the ink droplet LA to flow the ink L in an opposite direction from the ejection channel 60 to the supply channel 30. As a result, the ink L flows into the dead water region into which the ink L hardly flows in the normal mode, and the air bubbles in the ink L are reduced, so that the air bubbles accumulated in the dead water region can be reduced.

Description

  The present invention relates to a droplet discharge device.

  The ink jet recording apparatus of Patent Document 1 increases the flow velocity in the circulation channel by performing the suction purge by the suction purge device when performing the circulation purge excluding the bubbles in the circulation channel. The suction purge performed during the circulation purge is performed for a certain period from the beginning of the circulation purge.

  In the ink jet recording apparatus of Patent Document 2, when the ink is circulated in the circulation flow path connecting the print head and the ink tank and the circulation purge is performed to remove the bubbles in the flow path, the suction cap of the suction purge device is the print head. A closed space is formed so as to cover the nozzle surface. Then, the flow rate of the ink in the circulation channel is increased to such an extent that bubbles attached to the inner wall surface of the channel are easily removed.

  In the ink jet printing apparatus of Patent Document 3, ink is sent from a liquid chamber by a propeller, sent to a recording head via a supply tube, and returned to the liquid chamber by a return tube and circulated. The motor drive voltage is controlled to set the rotation speed of the propeller so that the delivered ink has a pressure that does not discharge from the nozzles.

Patent registration No.40551707 Patent registration No. 4179220 Japanese Patent Laid-Open No. 10-034899

  It is an object of the present invention to provide a droplet discharge device that can reduce bubbles accumulated in a circulation path or a dead water area of a droplet discharge unit while suppressing inadvertent liquid discharge from a discharge port in a bubble reduction mode. To do.

  A droplet discharge apparatus according to claim 1 of the present invention has a discharge port, a droplet discharge unit that discharges a droplet from the discharge port, and a supply path through which the liquid supplied to the droplet discharge unit flows A circulation path that circulates the liquid including a discharge path through which the liquid discharged from the droplet discharge section flows without being discharged from the discharge port, and the droplet discharge from the supply path. Driving means for selectively driving the liquid in one of a forward direction toward the discharge path via a section and a reverse direction from the discharge path toward the supply path via the droplet discharge section, and the discharge port A normal mode in which droplets are discharged from the droplet discharge portion while circulating the liquid in the forward direction while maintaining a negative pressure on the liquid surface, and a negative pressure on the liquid surface of the discharge port. Liquid without discharging droplets from the droplet discharge unit while maintaining the pressure. Switching between bubble reduction mode circulating in Kigyaku direction, having a mode switching means for circulating the liquid to the reverse direction by driving the driving means when the bubble reduction mode.

  In the droplet discharge device according to claim 2 of the present invention, the mode switching means switches from the normal mode to the bubble reduction mode while maintaining the pressure applied to the liquid level of the discharge port within a certain range.

  According to a third aspect of the present invention, in the normal mode, the liquid is circulated at the first speed in the forward direction, and in the bubble reduction mode, the liquid is circulated at the second speed in the reverse direction. The normal mode is performed subsequent to the bubble reduction mode, and the first speed is slower than the second speed.

  In the droplet discharge device according to claim 4 of the present invention, the supply path includes a common flow path, a plurality of individual flow paths connected to the common flow path and connected to the plurality of droplet discharge sections, A blocking means for blocking the flow of the liquid in the individual flow path, a bypass flow path that bypasses the droplet discharge section and connects the supply path and the discharge path is provided, and the bubble reduction In the mode, after the liquid is circulated in the reverse direction, the driving unit causes the liquid to flow through the bypass channel in a state where the blocking unit blocks the flow of the liquid to the plurality of droplet discharge units.

  In the droplet discharge device according to claim 5 of the present invention, a plurality of the droplet discharge units are connected to the supply path, and the bubble reduction mode is configured to supply liquid to some of the plurality of droplet discharge units. Includes partial circulation mode.

  In the droplet discharge device according to claim 6 of the present invention, the circulation path is provided with deaeration means for degassing from the liquid, and the mode switching means is configured to perform the deaeration in the normal mode and the bubble reduction mode. Pour liquid through the means.

  In the normal mode, the droplet discharge device according to claim 7 of the present invention is configured to discharge droplets from the droplet discharge unit while circulating the liquid in the circulation path, and the mode switching unit includes the bubble reduction mode. After performing this, the liquid is discharged from the discharge port without being circulated through the circulation path.

  In the droplet discharge device according to claim 8 of the present invention, at least one of the supply path and the discharge path is provided with a damper portion that reduces pressure fluctuation acting on the liquid, and the damper function of the damper portion is limited. Limiting means is provided, and the mode switching means operates the limiting means when performing the bubble reduction mode to limit the damper function of the damper portion.

  According to the first aspect of the present invention, it is possible to reduce bubbles by circulating a liquid via a droplet discharge unit without discharging a droplet from the droplet discharge unit in a state where the pressure applied to the liquid level of the discharge port is maintained at a negative pressure. Compared to the case where the mode is not provided, it is possible to reduce bubbles accumulated in the dead water area of the circulation path or the droplet discharge unit while suppressing inadvertent discharge of liquid from the discharge port in the bubble reduction mode.

  According to the second aspect of the present invention, compared with the case where the pressure applied to the liquid level of the discharge port is not maintained within a certain range when switching from the normal mode to the bubble reduction mode, the liquid is more carelessly discharged from the discharge port. It can be surely suppressed.

  According to the third aspect of the present invention, compared to the case where the first speed is equal to or higher than the second speed, it is possible to suppress the movement of the bubbles in the normal mode that is performed subsequent to the second bubble reduction mode.

  According to the fourth aspect of the present invention, it is possible to suppress the bubbles from staying in the common channel as compared with the configuration in which the driving unit does not flow the liquid in the common channel in the bubble reduction mode.

  According to the fifth aspect of the present invention, it is possible to suppress the bubbles from staying in the droplet discharge section as compared with the configuration in which the liquid is supplied to all of the plurality of droplet discharge sections at once in the bubble reduction mode.

  The invention of claim 6 can suppress the generation of bubbles when the temperature of the liquid rises as compared with the configuration in which the liquid does not flow through the deaeration means in the normal mode and the bubble reduction mode.

  According to the seventh aspect of the present invention, bubbles remaining in the droplet discharge portion can be removed as compared with the configuration in which the liquid is not discharged from the discharge port after the bubble reduction mode is performed.

  The invention of claim 8 makes it easier to move the bubbles as compared with the configuration in which the limiting means for limiting the damper function of the damper portion is not provided.

1 is a schematic diagram illustrating a configuration of an ink jet recording apparatus according to a first embodiment. It is a piping diagram of the ink jet head concerning a 1st embodiment. It is a block diagram of a control part which controls operation of an ink jet head concerning a 1st embodiment. (A) It is explanatory drawing which shows the pressure on the supply side, the pressure on the collection | recovery side, and a back pressure when starting the circulation of the ink in a forward direction in the head module which concerns on 1st Embodiment. (B) It is explanatory drawing which shows the pressure on the supply side, the pressure on the collection | recovery side, and a back pressure when starting the circulation of the ink from a forward direction to a reverse direction in the head module which concerns on 1st Embodiment. (A) It is explanatory drawing which shows the state which an ink flows in the forward direction in the circulation path which concerns on 1st Embodiment. (B) It is explanatory drawing which shows the state which an ink flows in the reverse direction in the circulation path which concerns on 1st Embodiment. (A) It is a schematic diagram which shows the state in which the dead water area was formed in the middle of the circulation path which concerns on 1st Embodiment. (B) It is a schematic diagram which shows the state through which the ink of the dead water area formed in the middle of the circulation path which concerns on 1st Embodiment flows. It is explanatory drawing which shows the state which an ink flows into a manifold and a 1st flow path in the circulation path which concerns on 1st Embodiment. It is explanatory drawing which shows the state which discharges ink from a head module after implementation of bubble reduction mode in the circulation path which concerns on 2nd Embodiment. It is explanatory drawing of the modification which shows the state which attracts | sucks ink from a head module after implementation of bubble reduction mode in the circulation path which concerns on 2nd Embodiment. It is explanatory drawing which shows the state which circulates ink to one part head module at the time of bubble reduction mode in the circulation path which concerns on 3rd Embodiment. It is explanatory drawing which shows the pressure of the supply side at the time of the bubble reduction mode in the head module which concerns on 3rd Embodiment, the pressure of a collection | recovery side, and a back pressure. It is explanatory drawing which shows the modification of the pressure of the supply side at the time of bubble reduction mode in the head module which concerns on 3rd Embodiment, the pressure of the collection | recovery side, and a back pressure. (A) It is a schematic diagram of the supply side subtank concerning 4th Embodiment. (B) It is a schematic diagram which shows the pressure fluctuation immediately after the exit of the supply side pump which concerns on 4th Embodiment. (C) It is a schematic diagram which shows the pressure fluctuation in the supply side manifold which concerns on 4th Embodiment. (A) It is a schematic diagram which shows the state which the film | membrane member of the supply side subtank concerning 4th Embodiment deform | transformed by the pressurization of the supply side pump. (B) It is a schematic diagram which shows the state which deform | transformed the film | membrane member of the supply side sub tank which concerns on 4th Embodiment, and closed the air connect valve.

(First embodiment)
An example of a droplet discharge device according to the first embodiment of the present invention will be described.

(overall structure)
FIG. 1 shows an inkjet recording apparatus 10 as an example of a droplet discharge apparatus that discharges ink droplets LA as an example of a droplet and records an image on a recording medium P. The inkjet recording apparatus 10 includes a storage unit 12 that stores a recording medium P, an image recording unit 14 that records an image on the recording medium P, and a transport unit 16 that transports the recording medium P from the storage unit 12 to the image recording unit 14. And a discharge unit 18 from which the recording medium P on which an image is recorded by the image recording unit 14 is discharged.

  The image recording unit 14 includes inkjet heads 20Y, 20M, 20C, and 20K. In addition, the inkjet heads 20Y, 20M, 20C, and 20K each have a nozzle 24 (see FIG. 2) as an example of a plurality of ejection openings. The nozzle surfaces 22Y, 22M, 22C, and 22K on which the nozzles 24 are provided have a recordable area that is about the same as or larger than the maximum width of the recording medium P.

  Further, the inkjet heads 20Y, 20M, 20C, and 20K are arranged in parallel in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the downstream side in the conveyance direction of the recording medium P. The ink drops LA corresponding to each color are ejected from a plurality of nozzles 24 (see FIG. 2) by a piezoelectric method, and an image is recorded on the recording medium P. In the following description, Y, M, C, and K alphabets are added to the reference numerals when it is necessary to distinguish the ink colors. In addition, when it is not necessary to distinguish the ink colors, the letters Y, M, C, and K may be omitted.

  The ink jet recording apparatus 10 is provided with a main tank 56 as a storage unit for storing ink L as an example of liquid for each color, and each ink jet from the main tank 56Y, 56M, 56C, 56K for each color. Ink L is supplied to the heads 20Y, 20M, 20C, and 20K. As the ink L supplied to the inkjet heads 20Y, 20M, 20C, and 20K, various inks such as water-based ink, oil-based ink, and solvent-based ink can be used.

  The conveying means 16 conveys the recording medium P to the take-out drum 28 for taking out the recording medium P in the storage unit 12 one by one and the ink jet heads 20Y, 20M, 20C, 20K of the image recording unit 14, and the recording surface (surface) ) To the inkjet heads 20Y, 20M, 20C, and 20K, and a delivery drum 32 that feeds the recording medium P on which an image is recorded to the discharge unit 18. The take-out drum 28, the transport drum 32, and the delivery drum 34 are configured to hold the recording medium P on the outer peripheral surface by electrostatic suction means or non-electrostatic suction means such as suction or adhesion. Yes.

  The take-out drum 28, the transport drum 32, and the delivery drum 34 are each provided with two sets of grippers 36 that hold the downstream end portion in the transport direction of the recording medium P at intervals in the circumferential direction. ing. The take-out drum 28, the transport drum 32, and the delivery drum 34 are configured to hold up to two recording media P on their outer peripheral surfaces by the gripper 36. The grippers 36 are provided in recesses 28 </ b> A, 32 </ b> A, 34 </ b> A formed on the outer peripheral surfaces of the take-out drum 28, the transport drum 32, and the delivery drum 34.

  Specifically, the rotation shaft 42 along the rotation shaft 38 of the take-out drum 28, the transport drum 32, and the delivery drum 34 is supported at predetermined positions in the recesses 28A, 32A, 34A. The shaft 42 is provided with a plurality of grippers 36 at intervals in the axial direction. Therefore, when the rotation shaft 42 is rotated in the forward direction (for example, clockwise direction shown in the figure) or the reverse direction (for example, counterclockwise direction in the figure) by an actuator (not shown), the gripper 36 is moved to the take-out drum 28, the transport drum 32, In addition, it rotates in the forward or reverse direction along the circumferential direction of the delivery drum 34, and holds or separates the downstream end in the transport direction of the recording medium P.

  That is, the gripper 36 rotates so that its front end part slightly protrudes from the outer peripheral surfaces of the take-out drum 28, the transport drum 32, and the delivery drum 34, so that the outer peripheral surface of the take-out drum 28 and the outer peripheral surface of the transport drum 32. The recording medium P is delivered from the gripper 36 of the take-out drum 28 to the gripper 36 of the transport drum 32 at a delivery position 44 where the two face each other. Further, the recording medium P is delivered from the gripper 36 of the delivery drum 32 to the gripper 36 of the delivery drum 34 at a delivery position 46 where the outer circumference of the delivery drum 32 and the outer circumference of the delivery drum 34 face each other.

  In addition, the inkjet recording apparatus 10 includes a maintenance unit (not shown) that maintains the inkjet heads 20Y, 20M, 20C, and 20K. The maintenance unit includes a cap that covers the nozzle surfaces 22Y, 22M, 22C, and 22K of the inkjet heads 20Y, 20M, 20C, and 20K, a receiving member that receives the ink droplet LA that has been preliminarily ejected (empty ejection), and the nozzle surfaces 22Y, 22M, and 22C. , A cleaning member for cleaning 22K, a suction device for sucking ink in the nozzles, and the like. Then, various maintenance operations are performed by moving the maintenance unit to a position facing the inkjet heads 20Y, 20M, 20C, and 20K.

(Image recording operation)
Next, an image recording operation of the inkjet recording apparatus 10 will be described.

  The recording medium P, which is taken out from the storage unit 12 one by one by the gripper 36 of the take-out drum 28 and held on the outer peripheral surface of the take-out drum 28, is conveyed while being attracted to the outer peripheral surface of the take-out drum 28. Then, at the delivery position 44, the paper is delivered from the gripper 36 of the take-out drum 28 to the gripper 36 of the transport drum 32. The recording medium P held by the gripper 36 of the transport drum 32 is transported to the image recording positions of the inkjet heads 20Y, 20M, 20C, and 20K while being attracted to the outer peripheral surface of the transport drum 32, and the inkjet heads 20Y, 20M, An image is recorded on the recording surface by ink droplets LA ejected from 20C and 20K.

  Subsequently, the recording medium P on which an image is recorded on the recording surface is transferred from the gripper 36 of the transport drum 32 to the gripper 36 of the delivery drum 34 at the transfer position 46. The recording medium P held by the gripper 36 of the delivery drum 34 is conveyed while being attracted to the outer peripheral surface of the delivery drum 34, and is discharged to the discharge unit 18. A series of image recording operations are performed as described above.

(Configuration of each part)
Next, the configuration of each part of the inkjet recording apparatus 10 will be described.

  FIG. 2 shows a piping diagram from the main tank 56 that stores the ink L to the inkjet head 20. The inkjet recording apparatus 10 includes a main tank 56 that stores ink L, a plurality of head modules 50 as an example of a droplet discharge unit that discharges ink droplets LA (see FIG. 1), and a circulation path 100 that circulates the ink L. And.

  In the circulation path 100, the ink L supplied to the head module 50 flows (the ink L flows from the main tank 56 to each head module 50), and the ink discharged from the head module 50 (without being discharged). And a discharge path 60 through which L flows. Each head module 50 is formed with a plurality of nozzles 24 from which ink droplets LA (see FIG. 1) are ejected, as described above. In the circulation path 100, the ink L flows from the supply path 30 via the head module 50 to the discharge path 60 in the forward direction, and the ink L flows from the discharge path 60 via the head module 50 to the supply path 30. The direction is the reverse direction.

  The supply path 30 includes a supply main pipe 98, a supply pipe 74, a supply side manifold 58 as an example of a common flow path, and a plurality of supply sides as an example of a plurality of individual flow paths connected to the supply side manifold 58. A branch path 62 is included. The discharge path 60 includes a recovery side manifold 64, a recovery side branch path 66, a recovery pipe 76, a recovery side main pipe 148, and a branch pipe 166 as an example of a common flow path to be described later.

  Each head module 50 is provided with an input port 52A through which ink L flows and an output port 52B through which ink L is discharged. The front end of the supply side branch path 62 branched from the supply side manifold 58 is attached (connected) to the input port 52A, and the front end of the recovery side branch path 66 branched from the recovery side manifold 64 is attached to the output port 52B. Connected (connected).

  That is, the supply side manifold 58 and the recovery side manifold 64 are connected to as many branch pipes (the supply side branch path 62 and the recovery side branch path 66) as the head modules 50 are installed. The ink jet recording apparatus 10 uses a predetermined pressure for the ink L supplied to the supply side manifold 58 (a pressure on the supply path 30 side, hereinafter referred to as a supply side pressure P1), and a predetermined flow rate. To supply to each head module 50. Further, the ink jet recording apparatus 10 uses the ink L supplied to the head module 50 at a predetermined pressure (pressure on the discharge path 60 side, hereinafter referred to as a pressure P2 on the recovery side) and a predetermined flow rate. In this structure, each head module 50 is recovered to the recovery side manifold 64.

  Here, in the head module 50, a differential pressure ΔP (= P 1 −P 2) is generated between the supply-side pressure P 1 and the recovery-side pressure P 2, whereby the supply-side pressure with respect to the nozzle surface 22 is generated. A back pressure P3 (P3 = (P1 + P2) / 2), which is an average pressure of the sum of P1 and the pressure P2 on the recovery side, is applied. The ink L is held by the plurality of nozzles 24 of the head module 50 by the back pressure P3. Then, by driving an energy generating element (not shown) for ink discharge, the ink droplet LA corresponding to the image information is discharged.

  The supply side branch path 62 is provided with a supply side valve 68 as an example of a blocking means for blocking the flow of the ink L in the supply side branch path 62 and a damper 70. Further, the collection side branch path 66 is provided with a collection side valve 72 and a damper 70 as an example of a blocking means for blocking the flow of the ink L in the collection side branch path 66. The supply side valve 68 and the recovery side valve 72 are opened and closed when the head module 50 needs to be individually operated, and the damper 70 is the ink L supplied from the supply side manifold 58 or the recovery side. It serves to alleviate pressure fluctuations during the flow of the ink L collected in the manifold 64.

  One end of a supply pipe 74 constituting a part of the supply path 30 is attached to one end in the longitudinal direction (the right end portion in FIG. 2) of the supply side manifold 58, and one end in the longitudinal direction is attached to the recovery side manifold 64. One end of a recovery pipe 76 that constitutes a part of the piping system for circulating the ink L is attached to the right end of FIG. Further, a first detour channel that bypasses the head module 50 and connects the supply channel 30 and the discharge channel 60 between the other end of the supply side manifold 58 and the other end of the recovery side manifold 64 is provided. A channel 78 and a second channel 82 are provided.

  A first valve 84 is provided in the first flow path 78. The second flow path 82 is provided with a second valve 86. The first flow path 78 and the second flow path 82 are used for pressure adjustment between the supply side manifold 58 and the recovery side manifold 64, ink flow rate adjustment, and the like. For example, in the normal circulation of the ink L (the flow of the ink L from the supply side manifold 58 to the recovery side manifold 64), the first valve 84 is closed and the second valve 86 is opened, and the ink L flows in the second flow. Only the road 82 can be distributed.

  Further, a supply-side pressure sensor 88 and a recovery-side pressure sensor 92 are attached to the other end of the supply-side manifold 58 and the other end of the recovery-side manifold 64, respectively. Thus, the pressure of the ink L flowing in the supply side manifold 58 and the recovery side manifold 64 is monitored. That is, based on the outputs of the supply-side pressure sensor 88 and the recovery-side pressure sensor 92, a pump control unit 212 (see FIG. 3), which will be described later, determines the rotation direction and rotation speed of the supply-side pump 118 and the recovery-side pump 149, which will be described later. Feedback control is performed to maintain a set differential pressure between the input port 52A and the output port 52B of the head module 50, and the ink L circulates.

  The other end of the supply pipe 74 connected to the supply side manifold 58 is connected to a supply side sub tank 94 as an example of a damper portion that reduces the pressure acting on the ink L. The supply-side subtank 94 has a two-chamber structure in which the inside is partitioned by an elastic film member 96. The lower side is an ink subtank chamber 94A and the upper side is an air chamber 94B.

  One end of a supply-side main pipe 98 for drawing ink L from a buffer tank 112 connected to the main tank 56 is connected to the ink sub tank chamber 94A. The other end of the supply-side main pipe 98 is connected to the buffer tank 112. An open pipe 95 is connected to the air chamber 94B. The open pipe 95 includes a supply-side air connect valve 97, a supply-side air tank 99, and a supply-side air tank 99 as examples of limiting means for limiting the damper function of the supply-side subtank 94. A supply-side air valve 101 is provided.

  In the supply side main pipe 98, the ink L is supplied to the degassing module 114, the one-way valve 116, and the head module 50 as an example of a degassing means for degassing from the inside of the ink L in order from the buffer tank 112 to the supply side subtank 94. A supply-side pump 118 that supplies pressure and supplies, a supply-side filter 122, and an ink temperature regulator 124 are provided.

  For example, the deaeration module 114 includes a two-layered cylinder (not shown), and this cylinder is formed of a film that allows only gas molecules to pass therethrough. In addition, a vacuum pump (not shown) having a function of changing the vacuum pressure is connected to the deaeration module 114, and the depressurization is performed in the deaeration module 114 by operating the vacuum pump, so that the inside of the ink L It is designed to degas bubbles.

  One end of the branch pipe 126 is connected to the inlet side of the supply side pump 118 separately from the supply side main pipe 98, and the other end of the branch pipe 126 is connected to the buffer tank 112 through the one-way valve 128. Yes.

  As an example, the supply-side pump 118 is configured by a tube pump using a stepping motor (not shown) (supplying ink L in the tube while squeezing an elastic tube by a rotational drive by the stepping motor). In particular, it is not limited to such a pump. In addition, one end of a drain pipe 132 is connected to the ink sub tank chamber 94 </ b> A, and the other end of the drain pipe 132 is connected to the buffer tank 112. The drain pipe 132 is provided with a supply-side drain valve 134.

  Since the supply side subtank 94 has a structure in which bubbles in the flow path are trapped by circulating the ink L, the supply side drain valve 134 is opened, and the supply side subtank 94 is driven by the driving force of the supply side pump 118. The bubbles are discharged from the buffer tank 112 opened to the atmosphere by being sent to the buffer tank 112.

  Next, the other end of the recovery pipe 76 connected to the recovery side manifold 64 is connected to a recovery side sub tank 142 as an example of a damper portion that reduces the pressure acting on the ink L. The collection-side sub tank 142 has a two-chamber structure in which the inside is partitioned by an elastic film member 144. The lower side is an ink sub-tank chamber 146A and the upper side is an air chamber 146B.

  One end of a collection-side main pipe 148 for drawing ink L into the buffer tank 112 is connected to the ink sub tank chamber 146A. An open pipe 152 is connected to the air chamber 146B. The open pipe 152 has a recovery-side air connect valve 154 and a recovery-side air tank 156 as examples of limiting means for limiting the damper function of the recovery-side subtank 142. , And a recovery-side air valve 158 is provided.

  The collection side main pipe 148 is provided with a collection side pump 149. Further, a pressure purge pipe 162 is provided between the inlet side of the recovery side pump 149 and the outlet side of the deaeration module 114 in the supply side main pipe 98. A one-way valve 168 and a recovery filter 170 are provided in order from the degassing module 114 to the recovery side pump 149 in the pressure purge pipe 162. That is, when reducing the bubbles by pressurizing the inside of the head module 50 and discharging the ink L at once, in addition to driving the supply side pump 118, the drive direction of the recovery side pump 149 is reversed with respect to the normal time. The degassed ink L is supplied from the buffer tank 112 to the recovery side manifold 64.

  Here, the supply-side pump 118 and the recovery-side pump 149 are provided in the circulation path 100 as described above, and drive the ink L from the supply path 30 to the discharge path 60 or from the discharge path 60 to the supply path 30. It is an example of the drive means (flow). The supply side pump 118 and the recovery side pump 149 have the same configuration.

  In the buffer tank 112, the main tank 56 and the ink L can be circulated by a replenishment pipe 172 provided with a replenishment pump 176. The buffer tank 112 stores an amount of ink necessary to circulate the ink L, and the ink L is replenished from the main tank 56 as the ink L is consumed. A filter 174 is provided at one end of the refilling pipe 172 (in the main tank 56). An overflow pipe 178 is provided between the buffer tank 112 and the main tank 56 so that the ink L is returned to the main tank 56 when the ink L is replenished excessively.

  One end of a branch pipe 166 is connected downstream of the recovery side pump 149 in the recovery side main pipe 148, and the other end of the branch pipe 166 is connected downstream of the replenishment pump 176 in the replenishment pipe 172. Yes. The branch pipe 166 is provided with a one-way valve 167.

  Here, the ink L in the collection side sub tank 142 is collected into the buffer tank 112 by the driving force of the collection side pump 149. In addition, one end of a drain pipe 147 is connected to the ink sub-tank chamber 146A, and the other end of the drain pipe 147 is connected to the drain pipe 132 through the recovery-side drain valve 151.

  Since the collection-side sub tank 142 has a structure in which bubbles in the flow path are trapped by circulating the ink L, the collection-side drain valve 151 is opened to drive the collection-side pump 149 with a driving force due to the reverse rotation. Bubbles in the collection-side sub tank 142 are sent to the buffer tank 112, and the bubbles are discharged from the buffer tank 112 that is open to the atmosphere.

  In the present embodiment, the pressure P1 of the supply side manifold 58 and the pressure P2 of the recovery side manifold 64 have a relationship of P1> P2, but each is a negative pressure supply. That is, the supply pressure of the supply side pump 118 is negative, but the recovery pressure of the recovery side pump 149 is further negative, so that the ink L flows from the supply side manifold 58 to the recovery side manifold 64 and the head module. The back pressure P3 of the 50 nozzles 24 is maintained at a negative pressure. Strictly speaking, as the elements of the back pressure P3, the height position of the supply side manifold 58 and the recovery side manifold 64, the ink flow rate, the flow path resistance, and the like are involved, so the pressure P1 on the input side and the pressure P2 on the output side. Should be taken into account when setting The back pressure P3 and the differential pressure ΔP are pressures in the vicinity of the nozzle 24 in the head module 50.

(Configuration of control unit)
Next, the control unit 200 of the inkjet recording apparatus 10 will be described.

  As shown in FIG. 3, the ink jet recording apparatus 10 includes a control unit 200 that controls the operation of each unit based on an input signal and discharges ink L from the head module 50 (see FIG. 2). .

  The control unit 200 includes a microcomputer 202, a head module control unit 204 connected to the microcomputer 202, a pressure control unit 206, a drain control unit 208, a pump control unit 212, and a temperature control unit 214. ing. The microcomputer 202 includes a CPU 216, a RAM 218, a ROM 222, an I / O unit 2, and a bus 226 such as a data bus and a control bus for connecting them.

  Here, the microcomputer 202 circulates the ink L in the forward direction with the head module 50 (see FIG. 2) maintaining the pressure applied to the liquid level of the nozzle 24 at a negative pressure, and the ink droplet LA (see FIG. 1), and the ink L (see FIG. 2) is circulated in the reverse direction without discharging the ink droplet LA from the head module 50 in a state where the pressure applied to the liquid level of the nozzle 24 is maintained at a negative pressure. It is an example of the mode switching means which switches the bubble reduction mode to be made. Then, the microcomputer 202 drives the supply side pump 118 and the recovery side pump 149 (see FIG. 2) in the bubble reduction mode, and supplies the supply path 30 (from the discharge path 60 (see FIG. 2) via the head module 50. Ink L is allowed to flow to (see FIG. 2). Further, the microcomputer 202 is set to flow the ink L through the deaeration module 114 in the normal mode and the bubble reduction mode. Further, the microcomputer 202 can switch from the normal mode to the bubble reduction mode while maintaining the pressure applied to the liquid level of the nozzle 24 within a certain range.

  A hard disk drive (HDD) 228 is connected to the I / O unit 224. Further, a supply side pressure sensor 88 and a recovery side pressure sensor 92 are connected to the I / O unit 224. Further, image data when an ink droplet LA is ejected from the nozzle 24 (see FIG. 2) of the head module 50 to form an image is input to the I / O unit 224 from the outside. Note that the image data may be data in which the ink ejection position and ejection amount are determined, or may be compressed data such as JPEG. Further, the CPU 216 reads and executes the ink circulation system program stored in the ROM 222.

  The ink circulation system program has a normal program for performing the above-described normal mode and a bubble reduction program for performing the above-described bubble reduction mode. As an example, the normal program causes the ink L in the buffer tank 112 shown in FIG. 2 to flow from the supply side manifold 58 to the recovery side manifold 64 and circulate, and the ink droplets LA (FIG. 1) according to the image data. A discharge program for discharging from the nozzle 24. The ink circulation system program is not limited to the ROM 222, but is stored in the HDD 228 or an external storage medium (not shown), and a network such as a reader or LAN (not shown) that reads information by loading the external storage medium. You may make it acquire from.

  As shown in FIG. 4, the CPU 216, based on the read circulation control program, the head module control unit 204, the pressure control unit 206, the drain control unit 208, the pump control unit 212, and the like connected to the I / O unit 224. The operation of the temperature control unit 214 is controlled.

  The head module control unit 204 discharges the ink droplet LA from the nozzle 24 (see FIG. 2) by the vibration of the pressure chamber by the energization control of the piezoelectric element or the like built in the head module 50. Device), supply side valve 68, recovery side valve 72, first valve 84, and second valve 86 are connected. Further, a supply side air connect valve 97, a supply side air valve 101, a recovery side air connect valve 154, and a recovery side air valve 158 are connected to the pressure control unit 206.

  A supply-side drain valve 134 and a recovery-side drain valve 151 are connected to the drain control unit 208. In addition, a supply side pump 118, a recovery side pump 149, and a replenishment pump 176 are connected to the pump control unit 212. Further, an ink temperature adjuster 124 is connected to the temperature control unit 214.

(Head module pressure setting)
Next, pressure setting in the head module 50 will be described.

  FIG. 4A shows changes in the supply-side pressure P1, the recovery-side pressure P2, and the back pressure P3 when the supply of the ink L in the forward direction is started in the circulation path 100 (see FIG. 2). It is shown. As described above, since the supply-side pressure P1, the recovery-side pressure P2, and the back pressure P3 are negative pressures, the pressure is more negative than 0 (atmospheric pressure state) (lower than 0 in the figure). Is set in

  As shown in FIG. 4A, the differential pressure ΔP and the back pressure P3 are substantially 0 [Pa] from time T0 to time T1. Then, the supply side valve 68 and the recovery side valve 72 (see FIG. 2) are opened at the time point T1, and the supply side pump 118 and the recovery side pump 149 (see FIG. 2) are operated between the time point T1 and the time point T2. Accordingly, the differential pressure ΔP is increased and the back pressure P3 is increased to the negative side, so that the forward circulation of the ink L in the circulation path 100 is performed after the time point T2. That is, the supply-side pump 118 and the recovery-side pump 149 correspond to the change rate (the slope of the graph from the time point T1 to the time point T2) in which the supply-side pressure P1 and the recovery-side pressure P2 are determined. In this case, the ink L is driven (flowed).

  Subsequently, as shown in FIG. 4B, the ink L is circulated in the forward direction until the time point T3 (the time point next to the time point T2). Here, when circulating the ink L in the reverse direction in the bubble reduction mode, the pressure P1 on the supply side is gradually increased and the pressure P2 on the recovery side is decreased from time T3 to time T5. That is, the supply-side pump 118 and the recovery-side pump 149 correspond to the change rate (the slope of the graph from the time point T3 to the time point T5) in which the supply-side pressure P1 and the recovery-side pressure P2 are determined. In this case, the ink L is driven (flowed). The back pressure P3 is not changed. At time T4 (T3 <T4 <T5), the differential pressure ΔP = 0.

  Subsequently, at time T5, the target circulation pressure in the reverse direction is reached. Then, the setting is such that the circulation of the ink L in the reverse direction is continuously performed from the time point T5 to the time point T6 at a predetermined flow rate. If the differential pressure between the supply-side pressure P1 and the recovery-side pressure P2 at time T3 is ΔP1, and the differential pressure at time T5 is ΔP2, | ΔP1 | <| ΔP2 | is set. The flow rate (speed) of the ink L increases as the differential pressure ΔP increases.

  That is, in the inkjet recording apparatus 10 according to the first embodiment shown in FIGS. 2 and 3, in the normal mode, the ink L is caused to flow from the supply path 30 to the discharge path 60 at the first speed V1, and in the bubble reduction mode, the discharge path 60. A supply side pressure P1, a recovery side pressure P2, and a back pressure P3 are set in the microcomputer 202 so that the ink L flows from the first to the supply path 30 at a second speed V2 that is faster than the first speed V1.

  Subsequently, as shown in FIG. 4B, the target circulation pressure in the reverse direction is maintained until time T6, and the supply side pressure P1 and the recovery side pressure P2 are gradually reduced from time T6 to time T7. At time T7, the differential pressure ΔP and the back pressure P3 are set to approximately 0 [Pa]. After time T7, the supply-side valve 68 and the recovery-side valve 72 of each head module 50 (see FIG. 2) are closed, and the air bubbles in other parts excluding the head module 50 are discharged.

  Further, as shown in FIG. 2, in the ink jet recording apparatus 10 of the first embodiment, the closed supply side valve 68 and the recovery side valve 72 supply the ink L to the plurality of head modules 50 in the bubble reduction mode. An operation program is set in the microcomputer 202 so that the supply-side pump 118 and the recovery-side pump 149 cause the ink L to flow through the supply-side manifold 58 and the recovery-side manifold 64 with the first valve 84 opened. Has been.

  Specifically, in the bubble reduction mode, after the ink L is allowed to flow from the discharge path 60 to the supply path 30 via the head module 50, the supply side valve 68 and the recovery side valve 72 cause the ink L to be supplied to the plurality of head modules 50. The supply-side pump 118 and the recovery-side pump 149 are set to flow the ink L through the first flow path 78 in a state where the flow is interrupted. Here, the bubble reduction mode in the first embodiment is the reverse circulation mode in which the ink L is circulated in the direction opposite to the normal mode as described above, and the supply side manifold after the reverse circulation mode as described above. 58 and a manifold bubble removal mode for flowing the ink L to the collection side manifold 64. In the inkjet recording apparatus 10 according to the first embodiment, after the bubble reduction mode is completed, the normal mode is continuously performed again.

(Function)
Next, the operation of the first embodiment will be described.

(Normal mode)
As shown in FIG. 5A, in the normal mode, when the supply side valve 68 and the recovery side valve 72 are opened, the ink 24 leaks and the air enters the nozzle 24 (see FIG. 2), and the ink L flows. It is necessary to suppress this. Therefore, the pump control unit 212 (see FIG. 3) operates the supply-side pump 118 and the recovery-side pump 149 (see FIG. 3), and the back pressure P3 is within a set range (for example, +100 when −3000 [Pa] or more). [Pa] or less, preferably −500 [Pa] or more and 0 [Pa] or less), and the differential pressure ΔP is controlled to be substantially 0 [Pa]. In this state, the head module control unit 204 opens the supply side valve 68 and the recovery side valve 72.

  In FIGS. 5A and 5B, reference numerals of parts necessary for the description and parts where the ink L flows are displayed, and reference numerals for parts not used in the description are omitted. 5A and 5B, the path through which the ink L circulates is indicated by a solid line, and the other paths are indicated by broken lines.

  Subsequently, the pump control unit 212 controls the operations of the supply-side pump 118 and the recovery-side pump 149, the back pressure is the target back pressure P3, and the differential pressure ΔP is the target differential pressure ΔP1 (see FIG. 4B). And Thereby, the buffer tank 112, the deaeration module 114, the supply side pump 118, the ink temperature adjuster 124, the supply side main pipe 98, the supply side sub tank 94, the supply pipe 74, the supply side manifold 58, the head module 50, and the recovery side manifold 64. The ink L is circulated (supplied) in the direction of arrow A (forward direction) in the order of the recovery pipe 76, the recovery side sub tank 142, the recovery side main pipe 148, the recovery side pump 149, the branch pipe 166, and the buffer tank 112. Then, the head module control unit 204 (see FIG. 3) operates the nozzle ejection device 51 (see FIG. 3) to circulate the ink L through the circulation path 100, and from the nozzle 24 (see FIG. 2) to the recording medium P. Ink droplets LA (see FIG. 1) are ejected (see FIG. 1).

  Here, as shown in FIG. 6A, when the stepped portion 103 is in the middle of the circulation path 100, when the ink L flows in the forward direction (the direction of the arrow A), for example, the corner 103A of the stepped portion 103 There may be a dead water area DE (a shaded area shown in the figure) inside the ink L that is difficult to flow (it is difficult to move along the flow FA of the ink L). Since the ink L stays in the dead water area DE, it is difficult to reduce bubbles contained in the staying ink L in the normal mode. Note that the dead water area DE may exist in the head module 50 in addition to the circulation path 100. Further, FIG. 6 is a schematic diagram to the last, and in which region the dead water area occurs depends on the shape of the circulation path 100 or the head module 50, the flow rate of the ink L, the direction of the flow of the ink L, and the like.

(Reverse circulation mode)
From the normal mode state shown in FIG. 5A, the pump control unit 212 (see FIG. 3) controls the operations of the supply-side pump 118 and the recovery-side pump 149 (see FIG. 2), and the back pressure P3 is set within a set range. The pressure difference ΔP is gradually reduced while being maintained within (for example, −3000 [Pa] to +100 [Pa], preferably −500 [Pa] to 0 [Pa]). And finally, it is set as the differential pressure ΔP2 (see FIG. 4B) that is in the opposite direction to the normal mode. As an example, the back pressure maintains the back pressure P3 in the normal mode as it is. For this reason, inadvertent ejection of the ink L from the nozzle 24 is more reliably suppressed.

  As a result, as shown in FIG. 5B, the buffer tank 112, the deaeration module 114, the pressure purge pipe 162, the recovery side pump 149, the recovery side main pipe 148, the recovery side sub tank 142, the recovery pipe 76, and the recovery side Manifold 64, head module 50, supply-side manifold 58, supply pipe 74, supply-side sub tank 94, ink temperature regulator 124, supply-side main pipe 98, supply-side pump 118, branch pipe 126, and buffer tank 112 in the order of arrow B Ink L is circulated (supplied) in the reverse direction. Note that the circulation of the ink L in the direction of the arrow B is performed in a time of 1 second to 300 seconds as an example.

  In the bubble reduction mode, the ink L sent from the recovery side pump 149 passes through the deaeration module 114. For this reason, in the inkjet recording apparatus 10, the degassed ink L is circulated in the reverse direction.

  Here, for example, as shown in FIG. 6B, when the ink L flows in the reverse direction (arrow B direction), the flow FB of the ink L passes through the dead water area DE inside the corner portion 103A of the stepped portion 103. To do. Thereby, the ink L staying in the dead water area DE flows, and the bubbles are moved from the dead water area DE of the circulation path 100 or the head module 50. Since the pressure applied to the liquid level of the nozzle 24 is maintained at a negative pressure, bubbles that accumulate in the dead water area DE of the circulation path 100 or the head module 50 while suppressing inadvertent ejection of the ink L from the nozzle 24 are suppressed. Decrease.

  Subsequently, after the circulation of the ink L in the reverse direction is completed, the pump control unit 212 (see FIG. 3) controls the operations of the supply side pump 118 and the recovery side pump 149 (see FIG. 2), and the back pressure P3. And the differential pressure ΔP2 is gradually changed, and finally the back pressure P3 is within a set range (for example, −3000 [Pa] or more and +100 [Pa] or less, preferably −500 [Pa] or more and 0 [Pa] or less) ), The differential pressure ΔP is set to approximately 0 [Pa], and the supply side valve 68 and the recovery side valve 72 are closed. Thus, the reverse circulation of the ink L in the bubble reduction mode is completed.

  In the ink jet recording apparatus 10 of the first embodiment, in the bubble reduction mode, the ink L flows from the discharge path 60 to the supply path 30 at a second speed V2 that is faster than the first speed V1 in the normal mode. Thus, in the bubble reduction mode, when the ink L is allowed to flow at the second speed V2 that is faster than the first speed V1 in the normal mode, the remaining bubbles that have not moved at the second speed V2 are the second speed V2. It is difficult to move in the normal mode of the first speed V1 that is slower than the first speed V1. Accordingly, it is suppressed that the bubbles in the dead water area DE move and the ink droplets LA including the bubbles are ejected in the normal mode performed after the bubble reduction mode.

(Manifold bubble removal mode)
As shown in FIGS. 3 and 7, in the inkjet recording apparatus 10 after the reverse circulation, the head module control unit 204 closes the supply side valve 68 and the recovery side valve 72. Thereby, the supply of the ink L to the plurality of head modules 50 is interrupted. Further, the head module control unit 204 opens the first valve 84, and the drain control unit 208 opens the recovery side drain valve 151. In FIG. 7, reference numerals of parts necessary for the description and parts where the ink L flows are displayed, and reference numerals of parts not used in the description are omitted. In FIG. 7, the path through which the ink L circulates is indicated by a solid line, and the other paths are indicated by broken lines.

  Subsequently, the pump control unit 212 drives the supply side pump 118 to flow the ink L through the supply side manifold 58 and the recovery side manifold 64 in the forward direction (arrow A direction). As an example, the speed at which the ink L flows is a speed close to the above-described second speed V2 (a speed faster than the first speed V1). Accordingly, the buffer tank 112, the deaeration module 114, the supply side pump 118, the supply side main pipe 98, the ink temperature regulator 124, the supply side sub tank 94, the supply pipe 74, the supply side manifold 58, the first flow path 78, the first flow path. Ink L circulates in the direction of arrow A (forward direction) in the order of the valve 84, the collection side manifold 64, the collection pipe 76, the collection side sub tank 142, the drain pipe 147, the collection side drain valve 151, the drain pipe 132, and the buffer tank 112 ( Supply).

  As described above, in the ink jet recording apparatus 10 of the first embodiment, in the bubble reduction mode, after the ink L is circulated in the reverse direction, the supply side manifold is shut off from the supply of the ink L to the plurality of head modules 50. The ink L is caused to flow through the recovery manifold 58 and the recovery side manifold 64. Thereby, even if bubbles moved from the dead water area DE during the reverse circulation of the ink L remain in the supply side manifold 58 and the recovery side manifold 64, they are moved and reduced by the flow of the ink L that does not pass through the head module 50. Therefore, air bubbles are suppressed from staying in the supply side manifold 58 and the recovery side manifold 64.

(Second Embodiment)
Next, an example of a droplet discharge device according to the second embodiment of the present invention will be described.

  The droplet discharge device of the second embodiment is mechanically similar to the inkjet recording device 10 of the first embodiment described above, and discharges the ink droplet LA from the head module 50 after the bubble reduction mode is performed. The configuration is different. For this reason, the second embodiment is also described as the ink jet recording apparatus 10, and the same reference numerals as those in the first embodiment are given to basically the same members as those of the ink jet recording apparatus 10 of the first embodiment described above. The description is omitted.

  As shown in FIG. 3, in the inkjet recording apparatus 10 of the second embodiment, the microcomputer 202 is configured to execute the normal mode, the reverse circulation mode, and the manifold bubble removal mode described above. Further, the microcomputer 202 is configured to eject ink L from the nozzles 24 (see FIG. 2) of the head module 50 after performing the bubble reduction mode of the first embodiment. Here, the bubble reduction mode in the second embodiment is an ink ejection mode in which the ink L is forcibly ejected from the head module 50.

(Function)
Next, the operation of the second embodiment will be described.

(Ink ejection mode)
As shown in FIGS. 3 and 8, in the inkjet recording apparatus 10, the head module control unit 204 opens the supply-side valve 68 and the pump control unit 212 drives the supply-side pump 118, thereby causing ink in the arrow A direction. L is supplied. Thereby, the ink L is ejected from the nozzle 24 without circulating the ink L through the circulation path 100. That is, the ink L remaining in the vicinity of the nozzle 24 and having increased viscosity and the bubbles contained in the ink L are discharged (removed) from the nozzle 24. In FIG. 8, reference numerals of parts necessary for the description and parts where the ink L flows are displayed, and reference numerals are omitted for parts not used in the description. In FIG. 8, the path through which the ink L circulates is indicated by a solid line, and the other paths are indicated by broken lines.

  The discharge of the residual ink L and the bubbles by supplying the ink L may be performed one by one for the plurality of head modules 50 or may be performed in a plurality of blocks. Further, the entire plurality of head modules 50 may be pressurized together. In addition, after the ink L is discharged, the ink L on the nozzle surface 22 (see FIG. 1) may be wiped off.

  As a modification of the inkjet recording apparatus 10 of the second embodiment, as shown in FIG. 9, a cap member 182 that covers the nozzle surface 22 of the head module 50, one end connected to the cap member 182, and the other end to the waste liquid tank 190. A connected waste liquid pipe 184, a suction selection valve 186 provided in the waste liquid pipe 184, and a suction pump 188 provided closer to the waste liquid tank 190 than the suction selection valve 186 of the waste liquid pipe 184 may be used.

  In the inkjet recording apparatus 10 according to the modified example, the microcomputer 202 opens the suction selection valve 186 and drives the suction pump 188 while the cap member 182 covers the nozzle surface 22, so that the inside of the cap member 182 is inside. Depressurized. As a result, the ink L remaining in the vicinity of the nozzle 24 and having increased viscosity and the bubbles contained in the ink L are discharged (sucked) from the nozzle 24.

  The discharge of the residual ink L and the bubbles by the inkjet recording apparatus 10 according to the modification may be performed one by one for the plurality of head modules 50, or may be performed in a plurality of blocks. Further, it may be carried out collectively for the plurality of head modules 50. In addition, after the ink L is sucked, the ink L on the nozzle surface 22 may be wiped off.

  As another modification, the ink L may be ejected from the nozzle 24 after the circulation of the ink L is started in the same sequence as in the normal mode.

(Third embodiment)
Next, an example of a droplet discharge device according to the third embodiment of the present invention will be described.

  The droplet discharge device of the third embodiment is mechanically similar in configuration to the ink jet recording device 10 of the first embodiment described above, and causes the ink L to flow through a part of the plurality of head modules 50. The configuration is different. For this reason, the third embodiment is also described as the ink jet recording apparatus 10, and basically the same members as those of the ink jet recording apparatus 10 of the first embodiment described above are given the same reference numerals as in the first embodiment. The description is omitted.

  As shown in FIG. 3, in the inkjet recording apparatus 10 of the third embodiment, the microcomputer 202 is configured to execute the normal mode, the reverse circulation mode, and the manifold bubble removal mode described above. Further, the microcomputer 202 is configured to perform control so that the ink L flows through a part of the plurality of head modules 50 in the above-described bubble reduction mode. That is, the bubble reduction mode in the third embodiment is a partial circulation mode in which the ink L is allowed to flow through a part of the plurality of head modules 50.

(Function)
Next, the operation of the third embodiment will be described.

(Partial circulation mode)
When the absolute value of the differential pressure ΔP2 during the reverse circulation of the ink L in the bubble reduction mode is larger than the absolute value of the differential pressure ΔP1 in the normal mode, the reverse circulation of the ink L is performed for all the head modules 50 at once. Then, since the flow rate of the ink L increases, there is a possibility that the liquid feeding capabilities of the supply side pump 118 and the recovery side pump 149 are insufficient. For this reason, in the inkjet recording apparatus 10 of the third embodiment, the plurality of head modules 50 are divided into a plurality of blocks, and the bubble reduction mode (reverse ink L) is provided for each block (part of the plurality of head modules 50). Directional circulation). In the present embodiment, two head modules 50 are described as one block as an example.

  As shown in FIGS. 3 and 10, from the normal mode state, the pump control unit 212 controls the operation of the supply side pump 118 and the recovery side pump 149, and gradually changes the back pressure P3 and the differential pressure ΔP, Finally, the back pressure P3 is set to 0 [Pa], and the differential pressure ΔP is set to 0 [Pa]. Then, the head module control unit 204 opens the supply side valve 68 and the recovery side valve 72 of the head module 50 corresponding to the first block, and supplies the supply side valve 68 and the recovery side valve 72 of the head module 50 of the remaining blocks. Close.

  Subsequently, the pump control unit 212 controls the operations of the supply-side pump 118 and the recovery-side pump 149, and the setting range in which the back pressure P3 does not become positive (as an example, −4000 [Pa] or more and 0 [Pa] or less). With the pressure maintained, the differential pressure ΔP is gradually reduced (the absolute value | ΔP | is increased) and finally set to −3400 [Pa] or less. Then, after reaching the final set differential pressure, the ink L is circulated in the reverse direction only for a set time (range is 1 second to 300 seconds, 60 seconds as an example).

  The ink L includes the buffer tank 112, the degassing module 114, the pressure purge pipe 162, the recovery side pump 149, the recovery side main pipe 148, the recovery side sub tank 142, the recovery pipe 76, the recovery side manifold 64, the head module 50, and the supply side. Circulation (supply) in the direction of arrow B (reverse direction) in the order of the manifold 58, the supply pipe 74, the supply side sub tank 94, the ink temperature regulator 124, the supply side main pipe 98, the supply side pump 118, the branch pipe 126, and the buffer tank 112. Is done. In FIG. 10, reference numerals of parts necessary for the description and parts where the ink L flows are displayed, and reference numerals for parts not used in the description are omitted. In FIG. 10, the path through which the ink L circulates is indicated by a solid line, and the other paths are indicated by broken lines.

  Subsequently, the pump control unit 212 controls the operation of the supply-side pump 118 and the recovery-side pump 149 to gradually change the back pressure P3 and the differential pressure ΔP, and finally the back pressure P3 is set to 0 [Pa], the difference The pressure ΔP is set to 0 [Pa]. Then, the head module control unit 204 closes the supply side valve 68 and the recovery side valve 72 of the head module 50 of the first block. These procedures are repeated from the head module 50 of the second block to the head module 50 of the last block.

  In FIG. 11, changes in the supply-side pressure P1, the recovery-side pressure P2, and the back pressure P3 are shown as timing charts. The ink L is circulated in the normal mode at time t0, and the back pressure P3 and the differential pressure ΔP are gradually brought close to 0 [Pa] from time t0 to time t1. At time t1, the back pressure P3 and the differential pressure ΔP are substantially 0 [Pa]. At this time, the supply side valve 68 and the recovery side valve 72 (see FIG. 10) of the other head modules 50 other than the first head module 50 (see FIG. 10) are closed.

  Subsequently, the set pressure is gradually changed from time t2 to time t3. Here, from time t2 to time t3, the rate of change of the pressure P1 on the supply side to the negative side is made larger than the rate of change of the pressure P2 on the recovery side to the positive side, so that the back pressure P3 becomes positive. The setting range is not maintained (for example, −4000 [Pa] or more and 0 [Pa] or less). After reaching the reverse circulation differential pressure ΔP2 at time t3, the reverse circulation is continued until time t4. Then, the set pressure is gradually changed from the time point t4 to the time point t5, and when the time point t5 is reached, the differential pressure ΔP becomes substantially 0 [Pa]. Here, the supply side valve 68 and the recovery side valve 72 of the head module 50 of the first block are closed, and the supply side valve 68 and the recovery side valve 72 of the head module 50 of the second block are opened.

  After that, each set pressure is changed at time points t6, t7, t8, and t9 in the same manner as at time points t2, t3, t4, and t5, and the blocks are changed sequentially until the last block (indicated by time points t10 and t11). Repeat the cyclic sequence. Finally, the set pressure is gradually changed to set the differential pressure ΔP and the back pressure P3 to approximately 0 [Pa]. Thereafter, the supply side valve 68 and the recovery side valve 72 of each head module 50 are closed, and the air bubbles in portions other than the head module 50 are discharged.

  In the timing chart shown in FIG. 11, after the back pressure P3 is changed toward the atmospheric pressure (0 [Pa]), the supply side valve 68 and the recovery side valve 72 (see FIG. 10) of each head module 50 are opened or Close. Thereby, in the inkjet recording apparatus 10, the leakage of the ink L from the nozzle 24 (see FIG. 2) and the mixing of bubbles are suppressed as compared with the case where each valve is opened or closed with the back pressure P3 in the normal mode. . In the present embodiment, the back pressure P3 when the reverse circulation is performed with the final set differential pressure ΔP2 in each head module 50 has the same value as the back pressure P3 in the normal mode.

  In FIG. 12, as a modification of the timing chart shown in FIG. 11, the back pressure P3 is in the normal mode including the timing when the supply side valve 68 and the recovery side valve 72 are opened or closed up to the head module 50 of the final block. A timing chart in the case of being maintained at the same pressure as the hour is shown. When the back pressure P3 is maintained in this way, there is little fluctuation in the pressure at the nozzle 24, so bubbles are less likely to enter the circulation path 100.

  At the time of reverse circulation, it is necessary to change the pressure of the supply side pump and the recovery side pump from the normal mode to the target pressure at the time of reverse direction circulation. However, as described above, in the inkjet recording apparatus 10 of the third embodiment, when the ink L is circulated in the reverse direction, the supply-side pump 118 and the recovery-side pump 149 can apply pressure to some of the head modules 50. Therefore, a desired target pressure can be easily obtained within the range of the capacities of the supply-side pump 118 and the recovery-side pump 149. Therefore, the supply of ink L to each head module 50 is suppressed from being insufficient, and bubbles are prevented from staying in the head module 50. Note that the second valve 86 may be closed.

(Fourth embodiment)
Next, an example of a droplet discharge device according to the fourth embodiment of the present invention will be described.

  The droplet discharge device of the fourth embodiment is mechanically similar to the inkjet recording device 10 of the first embodiment described above, and restricts the damper function of the supply side sub tank 94 and the recovery side sub tank 142. The configuration is different. For this reason, the fourth embodiment is also described as the ink jet recording apparatus 10, and the same reference numerals as those in the first embodiment are given to basically the same members as those of the ink jet recording apparatus 10 of the first embodiment described above. The description is omitted.

  As shown in FIG. 3, in the inkjet recording apparatus 10 of the fourth embodiment, the microcomputer 202 is configured to execute the normal mode, the reverse circulation mode, and the manifold bubble removal mode described above. Further, in the inkjet recording apparatus 10 shown in FIG. 2, the microcomputer 202 operates the supply side air connect valve 97 and the recovery side air connect valve 154 in the above-described bubble reduction mode, and supplies the supply side sub tank 94 and the recovery side sub tank 142. The damper function is limited. That is, the bubble reduction mode in the fourth embodiment is a damper function restriction mode for restricting the damper functions of the supply side sub tank 94 and the recovery side sub tank 142. Since the supply side subtank 94 and the collection side subtank 142 have the same configuration, only the collection side subtank 142 will be described here, and description of the supply side subtank 94 will be omitted.

(Function)
Next, the operation of the fourth embodiment will be described.

  In the inkjet recording apparatus 10 shown in FIG. 2, the supply-side pump 118 and the recovery-side pump 149 are configured by tube pumps as described above. The tube pump conveys the ink L by squeezing the tube with a roller. However, due to the structure, a fluctuation in pressure occurs as shown in FIG.

  Here, in the inkjet recording apparatus 10 shown in FIG. 2, by providing the supply side subtank 94 and the recovery side subtank 142 in the circulation path 100, these damper functions cause pressure fluctuations as shown in FIG. We are suppressing. 13B shows the pressure fluctuation immediately after the outlets of the supply side pump 118 and the recovery side pump 149, and FIG. 13C shows the pressure fluctuation in the supply side manifold 58 and the recovery side manifold 64. Is shown.

  FIG. 13A schematically shows the collection-side sub tank 142 and its peripheral part. In the normal mode, the membrane member 144 is located at the center in the collection-side sub tank 142, and maintains negative pressure and suppresses pressure fluctuation due to the damper function. In the normal mode, the collection side air connect valve 154 is opened, and the collection side air valve 158 is closed.

(Damper function restriction mode)
As shown in FIGS. 3 and 14A, before the bubble reduction mode (reverse direction circulation) is performed, the head module control unit 204 once closes the supply side valve 68 and the recovery side valve 72 to control the pump. The unit 212 operates the supply side pump 118 and the recovery side pump 149 to pressurize the inside of the circulation path 100 (see FIG. 2). By this pressurization, the membrane member 144 bends toward the air chamber 146 </ b> B, and finally sticks to the upper wall surface in the recovery-side subtank 142.

  In this state, as shown in FIGS. 3 and 14B, the pressure control unit 206 closes the recovery-side air connect valve 154. As a result, the membrane member 144 cannot move and the path to the recovery-side air tank 156 is blocked, so that the damper function of the recovery-side subtank 142 hardly functions (decreases).

  Subsequently, in a state where the damper function of the collection side sub tank 142 is limited, the pump control unit 212 operates the supply side pump 118 and the collection side pump 149 to circulate the ink L in the reverse direction.

  Here, in the inkjet recording apparatus 10 of the fourth embodiment, since the damper function of the collection side sub tank 142 is limited, the pressure fluctuation due to the pulsation of the collection side pump 149 is compared with that during normal circulation during the bubble reduction mode. Thus, it propagates into the circulation path 100 without being attenuated. Then, because of the pressure fluctuation, the bubbles staying in the circulation path 100 move, so that the bubbles in the circulation path 100 are easily moved.

  When returning to the normal mode, the supply-side valve 68 and the recovery-side valve 72 are once closed, the recovery-side air connect valve 154 is opened, and the pressure in the ink sub-tank chamber 146A is controlled. The collection side valve 72 may be opened.

  In addition, this invention is not limited to said embodiment.

  Collecting two or more of the first, second, third, and fourth embodiments, the ink droplet LA is ejected or sucked after the bubble reduction mode, or ink is applied to a part of the plurality of head modules 50 in the bubble reduction mode. L may be circulated, or the damper function of the supply side sub tank 94 and the recovery side sub tank 142 may be limited.

  The bubble reduction mode in the first embodiment includes the reverse circulation mode in which the ink L is circulated in the direction opposite to the normal mode as described above, and the supply-side manifold 58 and the post-circulation mode after the reverse circulation mode as described above. Although the manifold bubble removal mode for flowing the ink L to the collection side manifold 64 is included, the manifold bubble removal mode may be omitted. Moreover, after omitting the manifold bubble removal mode, the second to fourth embodiments may be combined with the first embodiment.

  When the ink L is circulated through a part of the plurality of head modules 50, for example, when there are 30 head modules 50, one block is divided into six blocks, and the ink L is circulated for each block. May be. The number of head modules in one block may be one or more.

  Both the supply-side subtank 94 and the collection-side subtank 142 do not have to have a damper portion, and it is sufficient that at least one of them has a damper portion.

10 Inkjet recording device (an example of a droplet discharge device)
24 nozzles (example of discharge port)
30 Supply path 50 Head module (an example of a droplet discharge unit)
58 Supply side manifold (example of common flow path)
60 Discharge path 62 Supply side branch path (an example of an individual flow path)
64 Recovery side manifold (example of common flow path)
68 Supply side valve (an example of shut-off means)
72 Collection side valve (an example of shut-off means)
78 1st flow path (an example of detour flow path)
94 Supply side sub-tank (example of damper part)
97 Supply-side air connect valve (an example of limiting means)
100 circuit 114 deaeration module (an example of deaeration means)
118 Supply side pump (an example of drive means)
142 Recovery side sub tank (an example of damper part)
149 Recovery side pump (an example of drive means)
154 Recovery side air connect valve (an example of limiting means)
202 Microcomputer (an example of mode switching means)
L ink (example of liquid)
LA ink droplet (an example of a droplet)

Claims (8)

A droplet discharge section having a discharge port and discharging a droplet from the discharge port;
A circulation path for circulating the liquid including a supply path through which the liquid supplied to the droplet discharge section flows, and a discharge path through which the liquid discharged from the droplet discharge section without being discharged from the discharge port;
One of a forward direction from the supply path to the discharge path via the droplet discharge section and a reverse direction from the discharge path to the supply path via the droplet discharge section provided in the circulation path Driving means for selectively driving the liquid;
A normal mode in which droplets are discharged from the droplet discharge portion while circulating the liquid in the forward direction while maintaining a negative pressure on the liquid level of the discharge port, and a liquid level of the discharge port Switching to a bubble reduction mode in which liquid is circulated in the reverse direction without discharging droplets from the droplet discharge unit while maintaining a negative pressure, and the driving means is driven in the bubble reduction mode. Mode switching means for circulating the liquid in the reverse direction;
A droplet discharge device having   2. The droplet discharge device according to claim 1, wherein the mode switching unit switches from the normal mode to the bubble reduction mode while maintaining a pressure applied to the liquid level of the discharge port in a certain range. In the normal mode, the liquid is circulated at the first speed in the forward direction,
In the bubble reduction mode, the liquid is circulated at the second speed in the reverse direction,
3. The droplet discharge device according to claim 1, wherein the normal mode is performed subsequent to the bubble reduction mode, and the first speed is slower than the second speed. The supply path includes a common flow path, a plurality of individual flow paths connected to the common flow path and connected to the plurality of droplet discharge units, and a blocking unit that blocks a flow of liquid in the individual flow paths. And provided,
A bypass flow path that bypasses the droplet discharge section and connects the supply path and the discharge path is provided,
In the bubble reduction mode, after the liquid is circulated in the reverse direction, the driving unit supplies the liquid to the bypass channel in a state where the blocking unit blocks the flow of the liquid to the plurality of droplet discharge units. The droplet discharge device according to any one of claims 1 to 3, wherein the droplet is discharged. A plurality of the droplet discharge units are connected to the supply path,
5. The droplet discharge device according to claim 1, wherein the bubble reduction mode includes a partial circulation mode in which a liquid is allowed to flow through a part of the plurality of droplet discharge units. The circulation path is provided with a degassing means for degassing from the liquid,
6. The droplet discharge device according to claim 1, wherein the mode switching unit causes a liquid to flow through the deaeration unit in the normal mode and the bubble reduction mode. 7. In the normal mode, the liquid droplets are ejected from the liquid droplet ejection unit while circulating the liquid in the circulation path,
7. The droplet discharge device according to claim 1, wherein the mode switching unit discharges the liquid from the discharge port without circulating the liquid in the circulation path after performing the bubble reduction mode. 8. . At least one of the supply path and the discharge path is provided with a damper portion that reduces pressure fluctuations acting on the liquid,
Limiting means for limiting the damper function of the damper portion is provided,
8. The droplet discharge device according to claim 1, wherein the mode switching unit operates the limiting unit to limit a damper function of the damper unit when performing the bubble reduction mode. 9.